1. A person weighs 155 lbs and is walking 3.1 miles per hour. How much kinetic energy does the person have? (Keep in mind, 1 kg is 2.2 lb, and 1 m/s is 2.24 mi/h.)2. What is the kinetic energy of a 5 g bullet travelling 400 m/s? 3. Is it possible to have a negative KE? Why or why not?

Explanation:

Kinetic energy is expressed as;

KE =1/2 mv²

M is the mass

v is the velocity of the object

1) Given

Mass = 155lb

Velocity = 3.1mi/hr

Since 1kg = 2.2lb

x = 155lb

x= 155/2.2

x = 70.45kg

Also

1m/s = 2.24mi/hr

y = 3.1mi/hr

y = 3.1/2.24

y = 1.384m/s

KE = 1/2(70.45)(1.384)²

KE = 0.9577×70.45

KE = 67.47Joules

2) M = 5g =0.005kg

V = 400m/s

KE = 1/2(0.005)400²

KE = 80000×0.005

KE = 400Joules

3} Since a body decelerates (negative acceleration) this mean that the velocity of a body can be a negative value showing that it is possible for a moving body to possess negative kinetic energy.

pythagoras' theorem

square root (-5^2+9^2)

square root (25+81)

square root (106)

angle is tan^-1(9/5)

neg x, pos y